Electromagnetic brakes of the type disclosed herein utilize spring means for applying compressive braking force to a non-rotatable armature and friction discs mounted on a rotatable shaft. Typically, the braking action prevents rotation of a drive means and a load driven by the drive means. The braking force is released by an electromagnetic force which causes compression of the brake spring and retraction of the spring away from the armature to release the spring's force on the armature and friction discs. After repeated operations of the brake, the friction discs will wear and become thinner. This permits the brake spring to expand and relax so that the compressive force of the spring on the armature and friction discs decreases. After sufficient wear of the friction discs, the brake spring force becomes inadequate to provide a minimum stopping and holding torque. If the friction discs are still usable, an adjustment is made on the brake spring to restore its compressive force on the armature and friction discs. If the friction discs must be replaced or if any other maintenance work must be done on the electromagnetic brake requiring release of braking force, the brake spring is moved to cause its release of force on the armature and friction discs.
One approach to adjusting the force of the brake spring is to provide, as part of the electromagnetic brake device, a threaded member which can be rotated against the spring brake or against other means engaging the spring. Rotation of the threaded member adjusts the compression of the spring in the direction of the armature and friction discs and thereby adjusts the spring braking force, i.e., the stopping and holding torque of the brake spring.
Approaches to release of the brake spring force and holding the spring released vary. The brake device may be partially disassembled to remove the brake spring. A threaded bolt may be inserted into a member bearing against the spring and the member moved against the spring by the bolt in a brake releasing direction. Lever and cam mechanisms may also be used to retract a member bearing against the spring in a brake releasing direction.
A drawback of presently known brake adjustment and releasing mechanisms is that no single mechanism is capable of both adjusting the brake spring force and also releasing the brake spring force entirely when necessary. Another problem is that many mechanisms, either of the adjustment or release type, are bulky and cumbersome to operate or require a certain amount of disassembling of the brake mechanism to provide the brake adjustment or release.